462 



H. H. NEWMAN 



TABLE 3 



Showing development of hybrids from F. diaphanus 9 X F. majalis d'; for control 

 see first column of table 1 



days 



1 week 



9 days 



12 days 



13 days 



14 days 



15 days 



16 days 



3 weeks 



First cleavage like control 



A smaller proportion of the more advanced stages of cleavage than 

 in control 



Blastoderm much smaller than in control, germ ring scarcely dis- 

 tinguishable, no embryonic shield (fig. 9) 



Germ ring one-third around the yolk, embryonic shield small and 

 only slightly elevated from germ ring, embryonic axis not estab- 

 lished (fig. 12) 



Blastopore still open, in some cases germ ring is only three-fourths 

 around yolk, optic vesicles flat with no optic cup, no lenses, no 

 enlargement of hind-brain, no chromatophores 



Embryo much less advanced than in control, no heart-beat, no body 

 or yolk pigment (fig. 15) 



Embryo about as advanced as control was at 4 days, chromato- 

 phores on head and yolk few as compared with control and all 

 more delicately branched as in paternal species, no vitelline cir- 

 culation but the majority of embryos have heart-beat established. 

 Nearly half of the embryos appear at this time as if they were 

 abnormal 



The normal embryos have developed very rapidly since the estab- 

 lishment of vitelline circulation and are now nearly on a par 

 with the control; many specimens, however, have failed to estab- 

 lish vitelline circulation and appear anemic and deformed 



Even the more advanced embryos have lagged behind control; a 

 number of abnormal embryos have died from anemia, the most 

 pronounced differences between hybrids and controls have to do 

 with pigmentation 



None hatched 



None hatched 



A very few hatched 



About a fourth hatched, larvae not very active 



Nearly all of the normally developing embryos hatched ; a few have 

 died without hatching 



Nearly all larvae dead, the few that have survived are not as large 

 or as vigorous as the pure bred larvae of the same age, living 

 under identical conditions 



